1. Field of the Invention
The present invention relates to a wireless communication network, more particularly to the access point apparatus in a wireless mesh network, and still more particularly to a method of establishing secure wireless links between access points.
2. Description of the Related Art
The mesh network architecture, which uses wireless links between access points, provides a simple and flexible way to extend the coverage area of a wireless local area network (LAN). Applications are expected to appear in homes, offices, college campuses, and other areas, and standardization of the architecture is under study by the Institute of Electrical and Electronics Engineers (IEEE) within the framework of the IEEE 802.11i group of wireless LAN standards.
Wireless LANs in general are at risk from eavesdropping, spoofing, and other well-known forms of tampering, including the setting up of unauthorized access points. In a mesh network these risks are increased, because access points can be set up almost without restriction and communications may be relayed over considerable distances. Authentication and protection of communication is therefore a critical issue, as discussed in, for example, Ji et al, ‘Self-Organizing Security Scheme for Multi-Hop Wireless Access Networks’, IEEE 2004 Aerospace Conference, Big Skye, Mont., March 2004, available as of Feb. 3, 2005 on the Internet at http://www.flacp.fujitsulabs.com/Aerospace04-51.pdf.
The above paper proposes an encryption key management system in which all access points in a network share a single group key distributed from a master access point. Consequently, if the group key is compromised at even one access point, the security of the entire network is endangered.
When this happens, it is necessary to halt all communication in the network and change the group key. Needless to say, this temporary shutdown of the entire network is a major inconvenience to network users. A similar inconvenience occurs when an access point is temporarily removed from the network for servicing or repair, because that involves a risk of possible key disclosure, and the group key must be changed to forestall the risk.
The inconvenience is particularly great when the network is large in scale or is connected to a wired network and forms part of the local infrastructure of the area in which it is used. Since mesh networks are expected to be large in scale and to operate in the infrastructure mode, there is an urgent need for a solution to this problem.
That is, from the standpoints of both network security and network operations, there is a need for wireless access point apparatus and connection processing methods that can establish secure wireless links between wireless access points without widespread sharing of encryption keys.